A history of spills and/or releases at two adjacent dry cleaning facilities near Houston, TX, resulted in significant soil and shallow groundwater contamination with PCE and daughter products. Soil was relatively permeable, with rapid groundwater flow beneath the site. A long, narrow, off-site plume extended beneath a residential neighborhood. Chemical oxidation was employed initially with only limited success in the areas of highest contamination. To take advantage of the soil permeability and other site conditions, the response action was amended to include enhanced aerobic bioremediation by cometabolism. Specialty microbes were introduced into the plume in several injections over a 15-month period. This approach achieved total contaminant level reductions in the source area from 1,600 to less than 40 µg/L, and at the front edge of the plume, levels decreased from 500 to 5 µg/L.
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